gnu: nomad: Update to 0.2.0-alpha-100-g6a565d3.

* gnu/packages/guile-xyz.scm (nomad): Update to 0.2.0-alpha-100-g6a565d3.
[source]: Use permanent redirect for source url.
[native-inputs]: Add gnu-gettext.
[inputs]: Add gstreamer, gst-plugins-base, gst-plugins-good, gst-plugins-bad,
gst-plugins-ugly.
[propagated-inputs]: Move to inputs gstreamer, gst-plugins-base, gst-plugins-good,
gst-plugins-bad, gst-plugins-ugly. Removed gsettings-desktop-scheme.
[arguments]: Set GST_PLUGINS_PATH, NOMAD_WEB_EXTENSION_DIR and GI_TYPELIB_PATH
variables in 'wrap-binaries phase.
[native-search-paths]: Remove it.

Signed-off-by: Mathieu Othacehe <othacehe@gnu.org>